If you drove around in 1980...in the regional town where I grew up, we had a total of maybe twenty grocery stores within a 20-mile circle. Today? There’s probably forty of them (one even specializing as bio or natural).
If downsizing did occur (over the $15 min wage), I don’t see grocery or food shortages occurring. You’d simply be correcting what was a poor design of big huge structures with a customer flow that didn’t meet the business requirements.
Now, if you said truckers are not happy with metropolitan deliveries (too much crime or looting), that would trigger a grocery/food crisis. Or if Biden triggered some farm crisis and prices suddenly escalated by 30-percent...that would also be different.
All of this chatter should focus on the fact that minimally-trained or minimally-capable workers aren’t worth $15 an hour, and the system will correct itself with these people being let go and finding no real job potential in the end.
The store model will probably go to what aldis does. Minimal employees, minimal service, minimal selection, minimal freshness.
You may not be aware of this, but in fast food chains across America, self serve kiosks have been appearing in anticipation of such a move.